Thread by @sophusticated

As new Biodiversity Net Gain #BNG consultation comes out today, here's where I stand on 5 key controversies based on our work building & analysing the Biodiversity Net Gain database looking at the effects of the policy using real data (e.g. in our paper conbio.onlinelibrary.wiley.com/doi/full/10.11…)

1) Stacking and bundling. It is in the best interest of landholders producing biodiversity units to allow stacking, as they call sell multiple credit streams from the same restoration efforts. But my take: this is actually not what's best for the policy as a whole - here's why

Landholders sometimes advocate for stacking arguing it's unprofitable to do restoration based on a single credit stream - only >1 will generate enough revenue to make it worthwhile. However, you have to weigh it up against what that money could have been spent on otherwise

With a finite restoration budget, if each project can stack & consume a larger share of budget, budget will be directed towards fewer sites in total. So whilst stacking might tip the economics of the occasional marginal site towards restoration, it probs delivers less overall

So in sum, I'd advocate bundling, but not stacking, on environmental grounds - even though landholders will likely be clamouring for stacking as it's in their self-interest

2) off-site vs on-site. As it stands, the vast majority of biodiversity units will be generated on-site according to our data (conbio.onlinelibrary.wiley.com/doi/full/10.11…). However, under the current governance regime, I *severely* doubt that on-site will deliver as it promises

In my view, developers & management companies will, on average, be under pressure from tenants to manage sites within the built environment for aesthetic purposes & not nature - think mown lawns people can play football on. Without proper independent enforcement from LPAs...

...over the 30 year timeline of biodiversity units, I expect the initial net gain plans for a development to slip away and the sites to managed for amenity purposes. This could be prevented by rigorous monitoring & enforcement, but LPAs are woefully underresourced

There's some, albeit old & small-sample, real data on this: sciencedirect.com/science/articl…. Authors re-visited grassland sites within developments promised in planning applications, & found 63% did not meet their stated ecological goals

I think the governance architecture for off-site gains is much more robust. So, without huge increases in LPA capacity & evidence enabling them to enforce on-site biodv gains, I would advocate for capping how much of your biodv liability developers are allowed to meet on-site

3) other species info. BNG MUST still account for the impact of a development on *species*, so ecological expertise is still essential. BNG must not be used as a justification for damaging species, compensated by creating habitat

I've seen this happen - I saw a development approved which built on turtle dove breeding territory, permitted *because* it delivered an increase in biodv units. So although it technicaly achieved a net gain in the Metric, it actually harmed threatened species. This can't happen.

4) Cost-shifting. UK spends just 0.023% GDP on nature conservation (nature.com/articles/d4158…). It's essential English gov't provides disaggregated stats on conservation spending, as my worry is that the gov't might cut funding for nature as the private sector spend on BNG rises

BNG as a whole offers no additionality if public sector cuts biodv spending & replaces with private spending. To be additional, the gov't must as a minimum maintain its core conservation spend whilst BNG draws private finance into compensating for the biodv damage of development

Why does this worry me? Cos we've seen this in other countries' compensation systems (e.g. @DivyaNarain1 @martine_maron show it here conbio.onlinelibrary.wiley.com/doi/full/10.11…)

5) Price ceilings. I hate the idea of price ceilings of biodv credits. If my understanding is correct, the gov't will provide statutory biodv credits as backup if no local units available. These need to be very high-priced we want the 'market' to work well for nature

Basically, the price of a credit should reflect its scarcity - how rare that habitat is. If you undercut that price by putting in a price ceiling, you're implicitly getting rid of the price info that's used to justify to use of a market for env protection in the first place

For these 'markets' to work for nature, they must disincentivise building where we damage a lot of biodv. Undercutting that price signal implicitly subsidises development in damaging areas. If these markets are working well for nature, sometimes credits will be really expensive

There are fundamental contradictions in offsetting markets - things that make them work well as *markets* (low transaction costs, high fungibility of credits) often contradict with their ecological aims (eg transactions costs are high if you're monitoring & enforcing properly!)

This is a tricky idea we've spent a lot of time thinking about - we (@martine_maron @CorletWalker @wildbusiness @RobertsonMorgan @J_Simmonds_AUS @StrangeNiels @Ascelin) wrote a paper about it here: sciencedirect.com/science/articl…

So, my opinion: for BNG to deliver good ecological outcomes - bundling, not stacking. Off-site over on-site. Still need to factor in other species info. Need disaggregated biodv spend accounting so we can monitor cost-shifting. And... I don't rate price ceilings.

Obv my views more nuanced than this & there's the occasional exception.

Consultation out today - respond! consult.defra.gov.uk/defra-net-gain…